A tappet of the pre-cited type is disclosed in DE-OS 41 11 610. An adjusting element extends through a bottom of the tappet and acts at one end on a closing member of a one-way valve of a clearance compensation element and cooperates at the other end with a groove on the outer peripheral surface of a contacting cam. This groove is arranged only on a small part of the outer peripheral surface of the cam and extends on both sides of the cam tip in the region of a lift-producing run-on and run-off flank of the cam. By an opening of the closing member outside of the region of the groove of the cam, it is intended to achieve any desired timing for valve intake and discharge. A more particular goal is to obtain an automatic shifting of the point of time of closing of the gas exchange valve concerned as a function of the engine speed.
However, this prior art document gives no incentive to the person skilled in the art as to how to relieve a high pressure chamber of the clearance compensation element during the cam base circle phase with the disclosed means in order to protect the gas exchange valve from camshaft displacements, torsional vibrations of the camshaft and other factors of influence such as circularity errors of the cam base circle which in the most unfavorable of cases can lead to the opening of the gas exchange valve concerned during the base circle phase.